根號(hào)下(1-2sina/2cosa/2)+根號(hào)下(1+2sina/2cosa/2)
=根號(hào)下(sin²(a/2)-2sina/2cosa/2+cos²(a/2))+根號(hào)下(sin²(a/2)+2sina/2cosa/2+cos²(a/2))
=根號(hào)下(sin(a/2)-cos(a/2))²+根號(hào)下(sin(a/2)+cos(a/2))²
=|sin(a/2)-cos(a/2)|+|sin(a/2)+cos(a/2)|
當(dāng)0原式
=-(sin(a/2)-cos(a/2))+(sin(a/2)+cos(a/2))
=2cos(a/2)
當(dāng)π/2≤a<π時(shí)
原式
=(sin(a/2)-cos(a/2))+(sin(a/2)+cos(a/2))
=2sin(a/2)